This invention relates to hand-pump spray bottles for dispensing a liquid in a jet or atomization mode and, more particularly, to such a hand-pump having a novel air inlet unit that prevents the liquid from leaking out of the air inlet unit when the container is operated at an orientation that causes the air inlet unit to be covered with liquid.
Hand-pump spray bottles have become increasingly popular to eliminate the use of pressurized cans due to environmental concerns and high cost. Over one billion spray bottles are sold each year to dispense such liquids as glass cleaners, bathroom cleaners, waxes and oils.
These spray bottles have a feed tube with an open distal end that extends into the liquid contents and serves as a conduit to the hand-pump. There is an air inlet port, usually located in the hand-pump, that admits air into the bottle during part of the pump suction and pressure discharge stoke. This admitted air replaces the liquid that is dispensed in order to maintain approximately atmospheric pressure with the bottle. These spray bottles operate well under some conditions. However, if the feed tube distal end is within the liquid and the air inlet port is covered with liquid, as would occur when the bottle is operated at certain commonly encountered orientations, the hand-pump will dispense the liquid satisfactorily but liquid will leak out of the air inlet port. This leakage occurs with conventional spray bottles as well as with any of the numerous bottles that can operate in the inverted position, such as described in U.S. Pat. Nos. 3,733,013; 4,775,079; and 5,624,060. This leakage is highly undesirable for any liquid since it is unpleasant to wet the hand and it is a waste of product. Any leakage, even the smallest amount, is completely unacceptable for any caustic liquids.
U.S. Pat. No. 4,072,252 discloses a hand-operated sprayer (FIG. 1 of the present drawings) that allows air to enter the bottle to replace the dispensed fluid in order to prevent the collapse of the bottle and to seal against liquid leakage from the bottle when the pump is not operated. This general concept is employed in most current trigger hand-pumps. Of particular and unique interest are passages 10 and 11 illustrated in FIG. 1 of the present drawings. The detailed description and operation of the '252 sprayer states that passage 10 in FIG. 1 (33 in the patent) "may be formed as a capillary tube of fine diameter whereby liquid leakage which might occur will be insignificant, yet air passage will be uninhibited." It will be shown in the detailed description of the present application that the short capillary tubes 10 and 11 of that prior art sprayer will not prevent leakage but merely restrict the quantity that is leaked.
U.S. Pat. No. 5,353,969 discloses a pump sprayer having a spiral vent path as shown in FIG. 2 of the present drawings. Like U.S. Pat. No. 4,072,252, the air vent restricts the liquid leakage by employing a small cross-sectional groove but additionally provides a long path to inhibit the flow of the liquid to the atmosphere. The spiral vent groove 21 illustrated in FIG. 2 is stated as having a length to restrict the free flow of liquid therethrough to avoid leakage and being sized so that, while dispensing in the inverted position, the rate of liquid discharge from the container is greater than the flow of air through the vent groove which thereby creates a vacuum in the container and effects a suck-back of air through the vent into the container. It will be shown in the following detailed description that the length of the spiral groove to prevent any leakage would have to be quite long and thus would not be practical for existing hand-pumps.
The aforementioned 366 parent patent discloses a hand-pump spray bottle that does not leak during hand-pump operation when held at an orientation where the liquid would normally contact the air inlet port. In that invention, the air inlet port is in circuit with a tubular section that acts as a holding volume for the liquid that would normally cover the air inlet port and leak to the atmosphere. Since the liquid is contained in the tubular section it will not leak into the atmosphere. While this invention will prevent leakage, the tubular section is too large to be accommodated in some hand-pumps. The size of the tubular section that is required in that invention is determined by the size of the air inlet port. When oriented so that liquid contacts the tubular section and the air inlet port is opened, as would occur during the operation of the hand-pump, the rate at which liquid enters the tubular section is controlled by the rate at which air flows out of the tubular section through the air inlet port to the atmosphere. The volumetric flow of air out of the tubular section through the air inlet port is inversely proportional to the square root of the density of the air. Since the density of the air is small compared to the liquid density, the size of the tubular section must be relatively large when controlled by the size of the air inlet port as compared to being controlled by a liquid orifice as in this invention. Since the minimum size of the air inlet port is limited by the manufacturing processes, the size of the tubular section is too large to be incorporated in some hand-pumps. The desirability of controlling the size of the tubular section (storage volume) by a liquid orifice rather than an air orifice will be made clear in the following description.
There is a need to provide an air inlet unit that can be incorporated into any hand-pump spray bottle that will admit air but will prevent any leakage of the liquid contents when the bottle is held at an orientation so that the air inlet port normally would be covered with liquid.